The present invention relates to an electrophotographic duplicating system comprising an electrophotographic copier and an option device or accessory for forming an enlarged or reduced image of a document set in the option device.
The copying apparatus represented by an electrophotographic copier has been used in many ways for the purpose of copying documents, and almost all of the copiers are constructed to obtain a life-size copy of the same document being copied. On the other hand, there are known copiers that print a reduced image of a large size document or an enlarged image of a microfilm is printed in an electrophotographic manner, but such apparatus is assembled in a copier as an inseparable device or in case of using it as an option device, use is made of the same optical path as that of the copier itself or use is made of a part of an optical path in common with the copier itself. It is a technique to assemble a reduction optical system in the copier itself inseparably, but the thus assembled apparatus becomes large and complicated. It is further known to detachably add an optical image projector to the copier itself as an option or accessory device, but such apparatus also has various defects. For example, in Japanese Patent Application Publication No. 4,944/67, Japanese Patent Application Publication No. 8,437/69, Japanese Patent Laid-open No. 62,724/76, Japanese Utility Model Laid-opn No. 127,827/77, Japanese Patent Laid-open No. 55,647/77 and the like, there is disclosed that the whole frame of a microfilm image is projected on a document table or a photosensitive member as a still picture by an option device and the projected image is scanned and exposed in the former apparatus by a scanning optical system, while in the latter apparatus the projected image is directly converted into an electrostatic latent image. However, the copier for copying the whole frame of a microfilm image projected as a still picture is large as the apparatus itself and lacks universality and convenience as compared with the copier of the document moving, scanning and exposing type which has recently been widely used. In the former system for projecting the microfilm image on the document table, when an enlarged image is projected by an option device, it is necessary to provide a long optical path in the device, so that the option device becomes disadvantageously large. Moreover in such known electrophotographic duplicating system comprising the electrophotographic apparatus and the option device for projecting the enlarged or reduced image of document, it is impossible to control the option device commonly by means of a sequence control circuit for controlling a duplicating operation of the copier without the option device, because the image of the document is projected from the option device onto a photosensitive member of the copier from a position which is different from an imaginary control start position of the photosensitive member in case of normal duplicating operation without the option device. Therefore it is necessary to provide a separate sequence control circuit. This causes the duplicating system to have a complicated construction and also increases the cost.